1. Field of the Invention
This invention relates to conversion adapters to be used for interconnecting optical connector ferrules having different diameters and methods for the production thereof.
2. Description of the Prior Art
In an optical connector which is used to facilitate the connection and the disconnection of two optical fibers or of an optical fiber and other optical element, like the SC type optical connector, for example, the predominantly used system comprises fitting one end of an optical fiber into an axial through-hole of a ferrule and inserting two ferrules thus prepared into an alignment sleeve through the opposite ends thereof to abut end faces of the ferrules against each other.
In order to directly align and connect the two ferrules to be connected by the above-mentioned system, it is necessary to align respective axes with very high accuracy because the diameter of a core thereof is small.
The use of the sleeve for aligning the ferrules each having an optical fiber inserted and fixed therein by abutting end faces thereof against each other includes the case where the optical connector plugs having the same ferrule diameter are mutually connected and the case where the optical connector plugs having different ferrule diameters are mutually connected. As a conversion adapter (sleeve) for connecting the optical connector plugs having different ferrule diameters, heretofore, those having the structures as shown in FIG. 1 through FIG. 5 are known in the art.
The conversion adapter 1 shown in FIG. 1 is a split sleeve comprising a large diameter part 2 having a large diameter through-hole xe2x80x9caxe2x80x9d, into which a large diameter ferrule 10 having an optical fiber 12 inserted and fixed therein is fitted, and a small diameter part 3 formed by reducing a diameter in one end portion of the large diameter part and having a small diameter through-hole xe2x80x9cbxe2x80x9d into which a small diameter ferrule 11 having an optical fiber 12 inserted and fixed therein is fitted, the sleeve having a slit 4 formed in the longitudinal direction thereof so as to elastically hold the ferrules 10 and 11 having different diameters. The large diameter part and the small diameter part are integrally formed of metal or plastic.
The conversion adapter 1 shown in FIG. 2, on the other hand, is a precision sleeve having a large diameter through-hole xe2x80x9caxe2x80x9d in a large diameter part 2 and a small diameter through-hole xe2x80x9cbxe2x80x9d in a small diameter part 3 formed in series along the axis thereof to form a step in the inside surface thereof. The large diameter part and the small diameter part are integrally formed of metal.
The conversion adapter 1 shown in FIG. 3 is a double tube type precision sleeve comprising a large diameter sleeve 2a made of metal and a small diameter sleeve 3a of metal fitted and fixed in one end part of the large diameter sleeve 2a. 
The conversion adapter 1 shown in FIG. 4 is a precision sleeve of the split sleeve type comprising a large diameter split sleeve 2a of metal having a slit 4 formed in the longitudinal direction thereof and a small diameter precision sleeve 3a of metal fitted and fixed in one end part of the large diameter split sleeve 2a. 
Further, Japanese Patent Application, KOKAI (Early Publication) No. (hereinafter referred to briefly as xe2x80x9cJP-A-xe2x80x9d) 9-90169 discloses a conversion adapter 1 comprising a large diameter part 2 into which a large diameter ferrule of an optical connector plug is fitted and a small diameter part 3 into which a small diameter ferrule is fitted, the large diameter part and the small diameter part being integrally formed of a synthetic resin such as, for example, a glass fiber-reinforced synthetic resin. The adapter has the structure such that a step is formed in the inside surface at the contact point between the large diameter part and the small diameter part and a groove 5 for air leakage is formed in the inside surface of the large diameter part in the axial direction thereof, as shown in FIG. 5.
As mentioned above, metal such as phosphor bronze and plastics as mentioned in JP-A-9-90169 are heretofore used as a material for the conversion adapter to be used for interconnecting the optical connectors having different ferrule diameters.
In the case of plastics, however, since they are deficient in mechanical strength and wear resistance, the decrease in the accuracy of the axial alignment of ferrules to be connected and the deformation or the deterioration of characteristics of the adapter itself are unavoidable in the conversion adapter to which attachment and detachment of the ferrule are repeatedly performed. Moreover, plastics have the difficulty that their resistance to weather (durability against the change in temperature or humidity) is low and they lacks in the reliability of prolonged use.
On the other hand, in the case of metal such as phosphor bronze, since the machining such as cutting should be performed to obtain the complicated shape like the conversion adapter, besides the above drawbacks, it takes much time to manufacture the conversion adapter and the cost of machining is large. As a result, the obtained product is inevitably expensive.
It is, therefore, an object of the present invention to provide a highly reliable and inexpensive conversion adapter which excels in mechanical strength and wear resistance, causes only sparingly deformation and wear even by repeated attachment and detachment of ferrules, and can maintain the accuracy of the axial alignment of ferrules for a long period of time.
A further object of the present invention is to provide a method which is capable of producing such an conversion adapter with high productivity at a low cost.
To accomplish the object mentioned above, in accordance with one aspect of the present invention, there is provided a conversion adapter to be used for connecting opposed optical connector ferrules having different diameters, which adapter is characterized by being formed of an amorphous alloy possessing at least a glass transition region, preferably a glass transition region of a temperature width of not less than 30K.
In a particularly preferred embodiment, the conversion adapter is characterized by being formed of a substantially amorphous alloy having a composition represented by either one of the following general formulas (1) to (6):
M1aM2bLncM3dM4eM5fxe2x80x83xe2x80x83(1)
wherein M1 represents either or both of the two elements, Zr and Hf; M2 represents at least one element selected from the group consisting of Ni, Cu, Fe, Co, Mn, Nb, Ti, V, Cr, Zn, Al, and Ga; Ln represents at least one element selected from the group consisting of Y, La, Ce, Nd, Sm, Gd, Tb, Dy, Ho, Yb, and Mm (misch metal: aggregate of rare earth elements); M3 represents at least one element selected from the group consisting of Be, B, C, N, and O; M4 represents at least one element selected from the group consisting of Ta, W, and Mo; M5 represents at least one element selected from the group consisting of Au, Pt, Pd, and Ag; and a, b, c, d, e, and f represent such atomic percentages as respectively satisfy 25xe2x89xa6axe2x89xa685, 15xe2x89xa6bxe2x89xa675, 0xe2x89xa6cxe2x89xa630, 0xe2x89xa6dxe2x89xa630, 0xe2x89xa6exe2x89xa615, and 0xe2x89xa6fxe2x89xa615.
Al100xe2x88x92gxe2x88x92hxe2x88x92iLngM6hM3ixe2x80x83xe2x80x83(2)
wherein Ln represents at least one element selected from the group consisting of Y, La, Ce, Nd, Sm, Gd, Tb, Dy, Ho, Yb, and Mm; M6 represents at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Hf, Ta, and W; M3 represents at least one element selected from the group consisting of Be, B, C, N, and O; and g, h, and i represent such atomic percentages as respectively satisfy 30xe2x89xa6gxe2x89xa690, 0 less than hxe2x89xa655, and 0xe2x89xa6ixe2x89xa610.
Mg100xe2x88x92pM7pxe2x80x83xe2x80x83(3)
wherein M7 represents at least one element selected from the group consisting of Cu, Ni, Sn, and Zn; and p represents an atomic percentage falling in the range of 5xe2x89xa6pxe2x89xa660.
Mg100xe2x88x92qxe2x88x92rM7qM8rxe2x80x83xe2x80x83(4)
wherein M7 represents at least one element selected from the group consisting of Cu, Ni, Sn, and Zn; M8 represents at least one element selected from the group consisting of Al, Si, and Ca; and q and r represent such atomic percentages as respectively satisfy 1xe2x89xa6qxe2x89xa635 and 1xe2x89xa6rxe2x89xa625.
Mg100xe2x88x92qxe2x88x92sM7qM9sxe2x80x83xe2x80x83(5)
wherein M7 represents at least one element selected from the group consisting of Cu, Ni, Sn, and Zn; M9 represents at least one element selected from the group consisting of Y, La, Ce, Nd, Sm, and Mm; and q and s represent such atomic percentages as respectively satisfy 1xe2x89xa6qxe2x89xa635 and 3xe2x89xa6sxe2x89xa625.
Mg100xe2x88x92qxe2x88x92rxe2x88x92sM7qM8rM9sxe2x80x83xe2x80x83(6)
wherein M7 represents at least one element selected from the group consisting of Cu, Ni, Sn, and Zn; M8 represents at least one element selected from the group consisting of Al, Si, and Ca; M9 represents at least one element selected from the group consisting of Y, La, Ce, Nd, Sm, and Mm; and q, r, and s represent such atomic percentages as respectively satisfy 1xe2x89xa6qxe2x89xa635, 1xe2x89xa6rxe2x89xa625, and 3xe2x89xa6sxe2x89xa625.
Furthermore, according to another aspect of the present invention, there is also provided a method of producing the aforementioned conversion adapter for the ferrules having different diameters.
One mode of the methods is characterized by comprising the steps of melting an alloying material capable of producing an amorphous alloy in a melting vessel having an upper open end, forcibly transferring the resultant molten alloy into a forced cooling casting mold disposed above the vessel and provided with at least one molding cavity, and rapidly solidifying the molten alloy in the forced cooling casting mold to confer amorphousness on the alloy thereby obtaining the product made of an alloy containing an amorphous phase.
In a preferred embodiment of this method, the melting vessel is furnished therein with a molten metal transferring member adapted to forcibly transfer the molten alloy upward, the forced cooling casting mold is provided with at least two identically or differently shaped molding cavities and runners severally communicating with the cavities, and the runners are disposed on an extended line of a transfer line for the molten metal transferring member.
Another method is characterized by comprising the steps of providing a vessel for melting and retaining an alloying material capable of producing an amorphous alloy possessing a glass transition region, providing a mold provided with at least one cavity of the shape of the product aimed at, coupling a hole formed in, for example, the lower or upper part of the vessel with a sprue of the mold, for example by disposing the mold beneath or on the vessel, then applying pressure on a melt of the alloy in the vessel thereby enabling a prescribed amount of the melt to pass through the hole of the vessel and fill the cavity of the mold, and solidifying the melt in the mold at a cooling rate of not less than 10 K (Kelvin scale)/sec. thereby giving rise to the product of an alloy containing an amorphous phase.
In any of the methods described above, as the alloying material mentioned above, a material having a composition represented by either one of the aforementioned general formulas (1) to (6) and capable of producing a product formed of a substantially amorphous alloy containing an amorphous phase in a volumetric ratio of at least 50% is advantageously used.
Still another method of the present invention is characterized by comprising the steps of heating a material formed of a substantially amorphous alloy having a composition represented by either one of the general formulas (1) to (6) mentioned above and containing an amorphous phase in a volumetric ratio of at least 50% until the temperature of a supercooled liquid region, inserting the resultant hot amorphous material into a container held at the same temperature, coupling with the container a mold provided with a cavity of the shape of the product aimed at, and forcing a prescribed amount of the alloy in the state of a supercooled liquid into the mold by virtue of the viscous flow thereof to perform molding.
By using an amorphous alloy capable of giving a cast product with high accuracy in accordance with the present invention, the adapters satisfying the dimensional accuracy and the surface quality required of the conversion adapters for connecting ferrules having different diameters can be manufactured with high productivity at a low cost by the mold casting method or molding method. Further, since the amorphous alloy to be used for the present invention excels in strength, resistance to wear, toughness, resistance to corrosion, and other properties mentioned hereinafter, the conversion adapters manufactured from this amorphous alloy withstand long service without readily sustaining abrasion, deformation, chipping, or other similar defects and are capable of keeping the high dimensional accuracy and holding the opposed ferrules stably for a long period of time as aligned mutually to their axes, even when the ferrules are repeatedly attached to and detached from the adapter, without injuring the ferrules and without rendering the development of backlash in the state of retention of ferrules.